Abstract

We analyze the effect of polarization-dependent loss (PDL) on the performance of the
polarization-division-multiplexed (PDM) signals in direct-detection systems. We
present the theoretical analysis of the sensitivity penalty caused by PDL-induced
coherent crosstalk and compare the results with experimental data obtained by using a
simple variable PDL emulator based on a LiNbO3 Mach-Zehnder modulator.
Also presented is the performance degradation caused by the polarization misalignment
between the received signals and the polarization beam splitter at the receiver in
the presence of PDL.

PDL-induced coherent crosstalk as a function of the angle between the polarization
state of PDM signal and principal axis of the PDL emulator. The PDL value was
changed from 1 to 5 dB by using the proposed PDL emulator.